Lol, theres nothing wrong with cruise control. Remember the zed is fly by wire anyway, theres no physical link between the ever trusty right foot and the throttle body, all the CC is doing is acting as the throttle pedal sending the same electrical signals to the throttle body as your foot would.
Its concerning it wouldn't turn off, very strange indeed, but I use mine on dual carriageway's especially when traveling at night as I can keep a perfect average speed and not get leg ache. Surely the brakes did something to retard the speed, I mean, its the same as applying the brakes when your accelerating, but it would have had some effect unless you have a brake issue, that is a physical link..
Id say the valuation is pretty good. I bought my 04 plate about 10-11 months ago for 6500. Only difference between mine and yours was the rays wheels. Mine was on 47,000 miles with full Nissan service history and some minor mods (powerflow exhaust, black vinyl roof)